The invention relates to power packs and, more specifically, to complex power packs with integrated cooling.
This application is related to application Ser. No. 09/040,112 filed Mar. 18, 1998 for "Semiconductor Power Pack" by Azotea et. al., the contents of which is incorporated herein in its entirety by reference.
Power pack manufacturers of today have not yet solved the built in problems of power pack geometries. These problems may include: suitable thermal management, "turn-off" inductance, and complicated device configuration.
In the power industry, issues concerning thermal interface, case temperature, and the cost of thermal management are generally not the responsibility of most manufacturers. A common practice in the power industry is to achieve maximum power levels by increasing the thermal gradient between the junction temperature of the silicon die and a "cold plate". Increasing the thermal gradient does not solve the underlying problem of an inadequate case-to-heat sink interface but adds cost and volume to the system design.
The forward blocking voltage (BVf) of power packs must be de-rated by the total internal inductance of the power pack multiplied by the rate of change of the peak turn-off current. The inductance values in power packs vary with geometry and are mostly a function of wiring length and mutual inductance.
Power packs having only one power device (e.g., one semiconductor power switch) may be referred to as power modules. A power pack may include plural power modules.
One known power module design includes a base plate, a lid, and a power device sandwiched between the lid and base plate. Such power modules may be single or double sided cooled but may not provide an optimum mounting and cooling area as compared to the total volume of the module.
For more complex power packs (i.e., two or more power devices in a power pack), the problems of providing a low volume package with suitable cooling (e.q., heat exchangers) and providing simultaneous operation of multiple power devices within a power pack having inductance remain.
One known technique for cooling involves attaching a heat exchanger to each individual power device in a power pack. The size and complexity of the power pack increases as the number of devices to be cooled increases, since each heat exchanger must have access to a coolant.
As for simultaneous operation of several power devices or even several power modules in one power pack, the driver circuitry may be located a distance away from the power device which increases the inductance of the power pack because of the extra lead length necessary to reach the power pack from the driver circuit. In parallel power device applications, the increased inductance may cause voltage over-shoot on turn-off which may damage power pack components.
Accordingly, it is an object of the present invention to provide a novel power pack.
It is another object of the present invention to provide a novel method of cooling a power device.
It is yet another object of the present invention to provide a novel heat exchanger.
It is still another object of the present invention to provide a novel method of cooling electronic devices.
It is a further object of the present invention to provide a novel method of providing structural support and cooling for heat generating electronic devices.
It is yet a further object of the present invention to provide a novel power pack having a heat exchanger as a chassis.
It is still a further object of the present invention to provide a novel power pack having increased power dissipation, decreased forward break down voltage derating factor, low inductance, and multiple power device configurations from the use of internal or external circuits.
It is yet still a further object of the present invention to provide a novel power pack in which a snubber capacitor may be implemented to limit the voltage over-shoot and to manage stray inductance. By locating the snubber cap on the cover and making the connection from the device to the snubber capacitor very short, coefficient of thermal expansion (CTE) problems are reduced, and less inductance between the power device and the capacitor is created making the snubber more effective. Additionally, the impedance may be matched.
It is yet still another object of the present invention to provide a novel power pack in which the cost is significantly reduced by mass producing the power device and effecting the configuration thereof by changing the external circuit.
These and many other objects and advantages of the present invention will be readily apparent to one skilled in the art to which the invention pertains from a perusal of the claims, the appended drawings, and the following detailed description of the preferred embodiments.